Creepy experiment
Male rats gave offspring during an experiment by Chinese scientists
Maria Azarova, Naked Science
Chinese scientists have reproduced a model of male mammalian pregnancy on laboratory rats: the results were only partially successful, but still showed that in such cases embryos can develop normally. The world community took the experiment with horror.
Male pregnancy is an extremely rare phenomenon in nature: it usually involves incubation of fetuses by males before birth, and needle (Latin Syngnathidae) is the only known family in which males bear offspring. In mammals, pregnancy is the responsibility of females. Nevertheless, scientists are still not definitively sure whether representatives of the "stronger sex" are really not capable of being pregnant.
Previous studies have shown that mouse embryos transferred to the genitals of males will develop in a limited stage, since this is hindered by certain factors. According to Chinese scientists from the Naval Medical University in Shanghai, the growth of embryos in the body of male mammals is hampered by two factors: the absence of a uterus and a specific microenvironment (dynamic levels of hormones and other molecules in the body).
The scientific group conducted an experiment on rats, which the Western media dubbed with horror as blatant and "Frankenstein". Animal experiments are usually needed to assess the safety of various drugs, because many such studies in one way or another worsen the quality of life of the living beings involved in them. In addition, tests on animal models have recently been considered a waste of time and money: about 95 percent of drugs tested in this way do not work for humans. Because of this, the US Department of Agriculture previously announced that some research on mammals would be phased out by 2025.
The work (Rongjia Zhang, Yuhuan Liu, A rat model of male pregnancy) is published on the preprint portal bioRxiv.org and has not yet been reviewed. So, in four stages, scientists managed to create a model of male pregnancy on Lewis laboratory rats.
Connection diagrams of female and male rats (drawings from the article in bioRxiv).
"Our experimental protocol included uterus transplantation and heterosexual parabiosis (two living organisms are surgically joined together so that they form unified common physiological systems. – Ed.). Uterus transplantation is a surgical procedure. Parabiosis is an experimental model that allows surgically connecting two animals and their circulatory system through anastomosis (connection, especially between vessels, hollow organs and cavities that are usually separated from each other or branching. – Ed.). The experiment consisted of four stages: 1) male rats were castrated, testicles, right ventral prostate gland and seminal vesicles were removed, and then paired with females to give a similar female microenvironment by blood circulation; 2) their uterus was transplanted; 3) embryos at the blastocyst stage were transferred to the transplanted uterus of males, and in order to compare the development, some of them were planted in the uterus of females; 4) caesarean section was performed for males," the authors of the study said.
Four stages of the experiment (photo).
When the males gave offspring, they were separated from the females. A total of 46 pairs and 842 embryos participated in the study (562 were transferred to female parabionts, 280 to male ones). Most died before birth: the fruits had a different shape and color, as well as atrophy or swelling of the placenta. Presumably, the abnormal death occurred at a late stage of development. 169 (30.07%) embryos developed normally in the native uterus of female parabionts, while only 27 (9.64%) in the transplanted male uterus. However, ten cubs born in this way still reached adulthood and had no health problems, the fathers who gave birth also felt fine. Thus, the experiment was successful by only 3.68 percent.
"We concluded that the normal development of embryos in male mammals depends on the mechanism that is associated with the effect of the blood of pregnant females. To test our assumption, 90 embryos at the blastocyst stage were transplanted only into the transplanted uterus of male parabionts: as a result, we did not find normal developing embryos in them," the experts summed up.
Four stages of the experiment (scheme).
Returning to the reaction of the world community: the study of Chinese scientists was opposed, including the organization for the protection of animal rights PETA (People for the Ethical Treatment of Animals). "After the males were castrated and forcibly bound to the female, their uterus was cut and implanted, embryos were placed in them – all in order to see if they could successfully produce offspring," said Emily McIvor, senior advisor for scientific policy at PETA. "Such astounding tests are dictated solely by curiosity and do not affect our knowledge of the human reproductive system in any way."
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